1. Field of the Invention
The present invention relates to a semiconductor device.
2. Description of the Related Art
Various types of semiconductor devices have been proposed that perform a specific function on the basis of inputs and outputs of a current from an external device, for example as disclosed in JP-A-No. 2002-76051. The conventional semiconductor device of this document includes a semiconductor element, a bonding pad, a protection layer, a wire, and a lead frame. The bonding pad is formed on the semiconductor element. The protection layer is also formed on the semiconductor element. The protection layer is located adjacent to the bonding pad, so as to cover the periphery of the bonding pad. The wire is bonded to the bonding pad and the lead frame.
The bonding pad is formed by stacking a metal, for example Al (aluminum). To bond a wire to the bonding pad, a wire, which is made of e.g. Cu (copper) and provided through a bonding tool such as a capillary, is molten and pressed against the bonding pad by the tip portion of the capillary, and ultrasonic vibration is applied. In this process, since Al is a relatively soft material, fragments of the bonding pad may disperse or the pad may crack due to the pressure and vibration applied during the wire bonding.
Further, in a conventional semiconductor device of JP-A-No. 2002-76051 (FIGS. 2 and 3), the periphery of the metal layer formed by stacking a plurality of metal films is covered with a protection layer, and the exposed portion of the upper face of the metal layer is serves as a bonding pad. With this configuration, however, the metal layer is formed over a larger region than the exposed portion as the bonding pad, which is disadvantageous to making the semiconductor device smaller in size. In addition, the protection layer covering the periphery of the metal layer may detach from the metal layer. When the underlying metal layer is exposed owing to the detachment of the protection layer, the uncovered portion of the metal layer may be corroded, and the durability of the semiconductor device may be degraded.